Causes of whooping cough

Whooping cough has a single direct cause: infection with the bacterium Bordetella pertussis. Everything else about 'causes' is really about how it spreads and who catches it.

The germ and its route. Bordetella pertussis attaches to the lining of the airways and releases toxins that paralyze the cleaning mechanism of the respiratory tract, causing the violent coughing. It spreads person-to-person through respiratory droplets - coughing, sneezing, close face-to-face contact, and shared indoor air. It is among the most contagious infections known: nearly everyone unvaccinated in a household catches it from a case.

The real-world source: faded immunity. Pertussis immunity - from vaccination or past infection - wanes over years. So the typical chain in a family is: a vaccinated-as-a-child adult or teenager with waning immunity gets what looks like a stubborn ordinary cough, and passes it to the youngest, most vulnerable member - an infant too young to be fully vaccinated. This is why 'cocooning' (vaccinating and treating the people around a newborn) is standard strategy.

Who is at risk of catching it: unvaccinated or incompletely vaccinated children; infants under six months; adolescents and adults whose vaccine protection has faded; anyone in close contact with a case during its first weeks, when it is most contagious (it looks like a mere cold then - the most infectious period is precisely when nobody suspects it).

What does not cause it: cold weather, bathing, sour food or any of the usual folk explanations. Crowding, poor ventilation and smoke exposure help the spread and worsen severity, but the bacterium is the cause.

Ayurvedic view (interpretive): classical attribution of severe cough to dosha disturbance is an interpretive framework of limited evidence; the bacterial cause and droplet route above are the established facts that drive prevention.

Remember: one bacterium, spread by droplets, most contagious when it looks like a cold, reaching babies through older family members with faded vaccine protection. Vaccination - including in pregnancy - breaks the chain.